An engine may include a turbocharger to increase air flow to the engine, thereby increasing power output by the engine. The turbocharger uses exhaust gas energy to turn a turbine and the turbine rotates a compressor via a shaft that connects the turbine to the compressor. Speed of the compressor influences air pressure in the engine's intake system. If compressor speed is higher than is desired, then pressure in the engine intake system may be higher than is desired. One way to limit compressor speed and engine intake system pressure is to install a wastegate with the turbocharger. The wastegate may allow a portion of exhaust gases to bypass the turbine to control turbine and compressor speed. The wastegate may be configured with a spring that holds the wastegate closed until pressure upstream of the compressor exceeds a threshold pressure, then the wastegate may open to limit or maintain compressor speed and engine intake pressure. However, it may be possible for the wastegate to be stuck in an open or closed state due to soot in the engine's exhaust system or degradation of the wastegate's components, such as the spring. If the wastegate is stuck in an open position, the engine may not be able to produce as much power as is desired. If the wastegate is stuck in a closed position, engine intake system pressure may be greater than is desired. Therefore, it may be desirable to provide a way of diagnosing a wastegate. However, if the wastegate is diagnosed while the engine is operating, engine performance may suffer or the vehicle may not perform in an expected way. Consequently, it may be desirable to provide a way of diagnosing a turbocharger wastegate without disturbing vehicle occupants or disturbing vehicle operation.
The inventor herein has developed an engine operating method, comprising: receiving sensor data to a controller and generating a wastegate diagnostic request via the controller; providing an indication of wastegate degradation based on intake manifold pressure, the intake manifold pressure sensed while rotating an engine in a reverse direction and not combusting air and fuel in the engine in response to the wastegate diagnostic request; and adjusting an actuator in response to the indication.
By rotating an engine in a reverse direction and measuring engine intake manifold pressure, it may be possible to provide the technical result of diagnosing turbocharger wastegate operation without disturbing vehicle occupants or compromising vehicle performance. In particular, the engine may be rotated in a reverse direction when the engine is not operating and a manifold absolute pressure (MAP) sensor may provide an indication of engine intake manifold pressure. The engine intake manifold pressure may indicate whether the wastegate is open or closed based on an amount of time it takes for engine intake manifold pressure to reach a threshold pressure after an intake throttle is closed from an open position. If it takes a longer than a threshold amount of time for engine intake pressure to reach the threshold pressure, the wastegate may be determined to be closed since closing the wastegate may restrict air flow from the exhaust system to the engine intake when the engine is rotated in a reverse direction. If it takes less than the threshold time for engine intake pressure to reach the threshold pressure, then it may be determined that the wastegate is in an open state since an open wastegate may be less restrictive to air passing through the exhaust system and into the engine intake when the engine is rotated in a reverse direction. In this way, it may be determined whether or not a wastegate is responding to opening and closing commands in an expected way.
The present description may provide several advantages. In particular, the approach may provide improved diagnostics of turbocharger wastegate operation. Additionally, the approach may assess wastegate operation with existing engine sensors so that diagnostics may not increase engine cost. Further, the approach may be accomplished while rotating the engine at lower speeds since air flow through the engine may be increased when the engine rotated in a reverse direction as compared to when the engine is rotated in a forward direction during similar conditions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.